In the conventional dental surgery and therapeutic process medical people often take a suitable treatment for a patient according to the condition of the patient's decayed tooth. In the event that the decayed condition is minor, a commonly called filling treatment usually is taken to prevent the decayed tooth from deteriorating. At the present filling treatment a filling material (such as dental amalgam, resin or ceramic artificial enamel) is filled in the patient tooth, then filling material is cured to finish the treatment. In the followings the resin is used as an embodiment of the filling material to facilitate discussion. In the filling treatment patient's tooth is cleaned first; next, a suitable amount of resin is filled in the tooth; then a dental light curing device is employed to provide a curing light to cure the resin.
Nowadays the technology of light-emitting diode (LED) is well developed, hence the LED also has been adopted in the dental light curing device. For instance, U.S. Pat. No. 7,094,054 discloses such a technique. During the filling treatment a high intensity curing light has to be generated to project the filling material for curing. Hence the LED also requires a greater amount of power to generate the curing light needed. As a result, a greater amount of waste heat also is generated from the LED. The aforesaid U.S. Pat. No. 7,094,054 discloses a dental curing light which includes a primary heat sink to hold the LED, an elongated secondary heat sink connected to the primary heat sink and an air fan installed corresponding to the secondary heat sink. Through a multi-stage heat exchange process the waste heat of the LED can be dispelled. In practice, the air fan is located on the secondary heat sink remote from the primary heat sink, and can only provide cooling airflow to do heat exchange for the surface of the secondary heat sink. The cooling efficacy is not desirable. Moreover, the secondary heat sink has a lengthy heat transfer path, and the air fan can perform the heat exchange merely for a single surface of the secondary heat sink. As a result, the waste heat generated by the LED still accumulates at one end of the secondary heat sink abutting the primary heat sink. Hence it still leaves a lot to be desired in terms of usability. In addition, the elongate secondary heat sink takes a greater portion of the interior space of the dental curing light that limits arrangement of other elements. This also makes changing the size and shape of the dental curing light to meet implementation requirements more difficult.